The problem of static electricity has become an ever increasing problem in environments where electronic equipment, such as computers and word processors, are in use. Basically, static is created when two similar materials are rubbed together and then separated. One object tends to give up electrons whereas the other tends to accumulate them, thereby leaving the former with a positive static charge and the latter with a negative charge. When oppositely charged objects contact each other, a static shock is created which corrects the imbalance.
Since the human body is almost a perfect conductor of electricity, studies of human movement in the office have shown that voltages in the range of 10,000 volts and higher can be generated. When discharged, these voltages can cause serious electrostatic damage to electronic components. A simple example of electrostatic discharge involves a person walking across a dry carpet in a dry atmosphere and touching a metallic object. The charge built up by the person moving across the carpet is retained throughout the person's body. As the person's hand reaches for the object a short distance away, the air's breakdown voltage is exceeded and an instantaneous blue arc occurs between the hand and the object. Interestingly, if breakdown voltage is not achieved (the charge generated is relatively small), the person will still discharge when touching the object. Particularly important is the fact that the person will not sense a discharge of less than 3500 volts. If this same person were reaching for an electronic component, such as a board or device on a grounded conductive table top, the discharge would occur through the component. Since many components and devices are sensitive to potentials far less than 3500 volts, the component could be damaged, and the person involved would have no way of knowing the cause.
Materials differ in their abilities to create and hold static charges, and over the years various expedients have been employed to provide anti-static properties. For example, substantial work has been done in the field of textiles, and also in other fields, including high pressure laminates and various types of cellulosic and non-cellulosic soft goods. Basically, these efforts have been directed to the use of additives such as metallic salts and carbon fibers. However, as applied to the decorative field, i.e., high pressure laminates, considerable difficulty has been experienced due to bleeding or blooming of the anti-static materials, particularly in the top or surface sheet of the laminate, thereby interfering with the coloring and/or decorative effects created on the top sheet. This is particularly true where the anti-static material contains a metallic salt. It has been found that where metallic salts are used, the anti-static properties of the laminate decrease in proportion to decreases in relative humidity, with the result that a laminate possessing the desired resistivity (ohms/square) at a relative humidity of 45-50% will be totally unsatisfactory at a lower relative humidity, as for example, below 35%. As a result, there has been no adequate solution to the problem of providing effective anti-static properties in resinous laminates.
Various anti-static chemical additives have been utilized for paper and for cellulosic and non-cellulosic non-woven disposable soft goods to minimize the discharge of static electricity, as encountered in high-speed printing and converting operations and also in the use of disposable soft goods, such as tissues. A product particularly suited for this purpose is LECTRAPEL.RTM. which is a water soluble polycationic quaternary ammonium polymer manufactured by Calgon Corporation. Applications of 0.0025 to 0.01 pound solids per 1000 square feet of paper, paperboard or non-woven textile fabric are the normal range in which this material is applied to the sheet being treated. Higher concentrations have not been recommended due to puddling of the material and the anticipated adverse effect on the ability of the treated sheet to be saturated with resin or other desired saturants. Consequently, materials such as LECTRAPEL.RTM. have hitherto been regarded as unsuitable for use in high pressure laminates.